The present invention relates to a product to prevent the presence of and/or to destroy termites as well as a process for implantation of this same product.
The propagation of termites nowadays requires preventive treatment of constructions, particularly buildings. This preventive treatment is carried out by the formation of horizontal and vertical barriers at the base of walls and in the walls themselves of the constructions. These barriers are nowadays produced by injection in the soil and in the walls, of an aqueous dispersion of a powerful insecticide powder.
The use of an aqueous dispersion has major drawbacks. Thus, it is known that the effective life of the treatment is not very long in the soil because, after treatment, the powder is easily entrained in rainwater. The effectiveness of the treatment is thus reduced. Moreover, the entrainment of the insecticide at a point distant from the site to be treated can give rise to subsoil pollution, in particular in the case of the presence of a phreatic layer. As a result, any overdosage which could be envisaged to improve the effective life of the treatment must be precluded. Moreover, the implantation of an aqueous dispersion in places with variable absorption properties, arising for example from the nature of the materials delimiting the emplacement, does not permit precise dosage of the truly active quantity of insecticide. Finally, the absence of controlled release of the active substance in the liquid state requires, for effectiveness over several years, the use of large quantities of active substance.
Compositions permitting controlled release of an insecticide have however been conceived. Such is the case of the composition described in U.S. Pat. No. 4,400,374. This floating composition, because destined for aquatic media, comprises a polymer, an active substance and a porogenic agent adapted to create a porous network within the polymeric matrix to permit water of the surrounding medium to come into contact with the active substance freed from the polymer. The kinetics of slow and progressive release thus obtained do not permit application of this composition for curative purposes. Moreover, the presence of the porogenic agent requires an environment with a high water content to be effective.
Other compositions are known, based on a polymer and an insecticide for various applications such as the protection of cables (GB-A-2.276.171) or of wood base material (W097/37543). These compositions again do not permit preventive and curative treatment against termites.
A first object of the invention is to provide a product to destroy termites, whose design permits preventive and curative treatment against termites with a reduced initial quantity of active substance.
Another object of the present invention is to provide a product for destroying termites, whose design permits limiting the loss of the active substance in the ground or in the walls of the construction to be protected, and to reduce the quantity of active substance initially introduced into the product whilst preserving a high effectiveness of treatment over a long period of time.
Another object of the present invention is to provide a product to destroy termites, whose design permits on the one hand limiting the risk to the environment, in particularly by avoiding migration of the active substance through the phreatic layer by leaching, on the other hand to enclose totally the construction or the region to be protected.
Another object of the present invention is to provide a product to destroy termites, whose design permits easier handling and storage.
To this end, the invention has for its object a termicidal product to prevent in a prolonged manner the presence and/or to destroy termites, in a suitable environmental medium by placing the product into contact with said medium, said product containing at least one active substance to destroy termites, characterized in that it has the form of a generally elongated solid body constituted
a) of a core in the form of an extrusion or molding or sinter and constituting a solid macroscopic matrix which degrades under the influence of the environmental medium, generally by biodegradation and/or biodispersion and/or solubilization and/or chemical or physical degradation, this core being based on at least one binding polymer preferably extrudable and at least one substance active against termites releasable into the environmental medium over a period of time T2.
b) an envelope about the core, containing at least one substance active against termites, this active substance of the envelope being releasable, into the environmental medium, at least under the influence of moisture of the environmental medium and/or a liquid introduced into said medium, according to a release profile such that, when the product is exposed to an environmental medium with a substantially constant moisture content near than 100%, the quantity of active material released per unit time into the environmental medium by the envelope decreases in the course of time over a predeterminable period of time T1, after an induction period T0, this time period T1 corresponding at most to T2 to give rise by means of the envelope to an initial rapid release of the active substance for a curative effect against termites and by means of the core a slow and prolonged release of the active substance for preventive effect against termites.
The inventors have determined that it is necessary to release over a short time a large quantity of active substance to obtain the curative effect then, to obtain preventive effect against a reinfestation by termites, to release slowly over a longer period of time a quantity of active substance so as to maintain in the environmental medium a quantity of active substance greater than or equal to the lethal dose. This curative effect is caused by the envelope of which at least one portion of the constituents soluble in water or in any liquid, permit the release over a short time of a large quantity of the active substance. Conversely, the preventive effect is performed by the core in which the polymer present slows the physical, chemical and/or enzymatic degradation of the core such that the release of the active substance can extend over a period at least equal to two years, the active substance of a core coming progressively to replace in the environmental medium the active substance released by the envelope. This design moreover permits reducing the quantity of active substance initially present in the product. Finally, the release of the active substance, relying essentially initially on the moisture of the environmental medium and thereafter on the moisture augmented by other parameters, such as the presence of microorganisms, the pH, the temperature . . . , is guaranteed. This release of the active substance can take place by slow dissolution, by diffusion and/or by erosion. Moreover, as termites grow essentially in moist media, the design of the product is perfectly adapted to these latter.
Finally, thanks to the preparation of the product in the form of a solid product, the quantity of active substance delivered is carried out in a sure manner, the risk of migration of the product into rainwater are reduced and the implantation of the product is facilitated.
The invention also has for its object a process for the implantation of a product for destroying termites in any location of a site to be protected, characterized in that it consists, in any order, on the one hand of carrying out an application of liquid, such as water, to or in the vicinity of the emplacement destined to receive the product according to the above definition, on the other hand in positioning said product in said emplacement.
The invention will be better understood from a reading of the description with embodiments and the single figure which represents the kinetic of liberation of the active substance contained in the envelope in suitable environmental medium.
The product to destroy termites, called a termicide, which is the object of the invention, comprises at least one active substance for the destruction of termites. This active substance must satisfy a certain number of criteria. This active substance must in particular be stable at temperatures of production of the product, remain stable and active within the normal pH range that is found in constructions or in the soil, and, of course, have the ability to destroy termites. The active substance used in the product is preferably selected from the group of substances formed by BENDIOCARB (trade mark) made by NOR-AM CHEMICAL Co., ISOFENPHOS (trade mark) made by MOBAY CHEMICAL Co., FENVALERATE (trade mark) made by ROUSSEL BIO Corporation, phenyl-pyrazole compounds, in particular FIPRONIL (trademark) made by Rhone-Poulenc responding to the molecular formula C12H4Cl2F6N4OS, organochlorine compounds, such as ENDOSULFAN (trademark) made by ROUSSEL BIO Corporation, synthetic pyrethrinoide compounds, in particular BIFENTHRINE (trademark) made by FMC CHEMICAL Co., CYPERMETHRINE (trademark) made by ICI CHEMICAL Co. and FMC CHEMICAL Co., DELTAMETHRINE(trademark), ALPHAMETRINE(trademark), organophosphorus compounds such as CHLORPYRIFOS (trademark) made by DOW ELANCO and the pyrrol compounds such as CHLORFENAPYR (trademark) made by Cyanamid Agro.
As mentioned above, the product to destroy termites, which is the object of the invention, is constituted by a core and an envelope which each contain a substance active against termites, these actives substances of the envelope and of the core being of identical or different nature.
The core is obtained by shaping generally by extrusion, molding or sintering of at least one polymer binder, preferably extrudable, and a substance active against termites to form a solid macroscopic matrix giving to the product a mechanical strength sufficient to permit ultimately the implantation of the product in the soil or in a construction constituting the environmental medium to be protected against termites.
The polymer or polymers constituting the core are a function of the substance used that is active against termites. Generally, the polymeric binder, preferably thermofusible, present individually or in the form of a mixture in the matrix of the core, is selected from the group consisting of vinyl and polyolefin polymers and copolymers, acrylic polymers and copolymers, polyamids, polyesters, silicon and insoluble cellulosic derivatives, such as cellulose diacetate and cellulose acetate and polyurethanes.
It is to be noted that to facilitate the release of the active substance from the matrix, the matrix can moreover comprise hydrophilic substances which promote the absorption of water into the matrix.
In the case of formation by extrusion or molding, the core is constituted:
from 1 to 40% by weight, preferably 5 to 25% by weight, of a substance active against termites and
from 60 to 99% by weight, preferably 75 to 95% by weight, of polymers and if desired additives such as a porous filler, starch or a plasticizer, and in that, in the case of a sintered embodiment, the core is constituted:
from 1 to 99% by weight, preferably 10 to 70% by weight, of active substance and
from 1 to 99% by weight, preferably 30 to 90% by weight, of binder polymer and additives.
In what follows, a first embodiment of a core involves the incorporation of THERMIDOR 80 WG (trademark) (concentrated to 80% in FIPRONIL) in said core.